Turbo fluid machine

ABSTRACT

A turbo fluid machine includes: a housing; an electric motor; an impeller that compresses fluid; and a drive shaft connecting the impeller and the electric motor in the housing. The impeller chamber includes a first impeller chamber and a second impeller chamber distanced from each other in an axial direction of the drive shaft. The impeller includes: a first impeller that compresses the fluid to produce first compressed fluid; and a second impeller that compresses the first compressed fluid to produce second compressed fluid. The turbo fluid machine further includes: a compressed fluid passage through which the first compressed fluid is supplied to the second impeller chamber; and a plurality of flow straightening passages that extends inside the compressed fluid passage in a direction in which the compressed fluid passage extends, and through which the first compressed fluid is straightened and supplied to the second impeller chamber.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims priority to Japanese Patent Application No. 2022-022811 filed on Feb. 17, 2022, the entire disclosure of which is incorporated herein by reference.

BACKGROUND ART

The present disclosure relates to a turbo fluid machine.

Japanese Patent Application Publication No. 2015-187444 and Japanese Patent Application Publication No. H08-200296 disclose a conventional turbo fluid machine. The turbo fluid machine of Japanese Patent Application Publication No. 2015-187444 includes a housing, an electric motor, an impeller, a drive shaft, and a compressed fluid passage. The housing includes an impeller chamber and a motor chamber. The impeller chamber includes a first impeller chamber and a second impeller chamber distanced from the first impeller chamber in an axial direction of the drive shaft. The motor chamber is disposed between the first impeller chamber and the second impeller chamber. The electric motor is accommodated in the motor chamber.

The impeller includes a first impeller accommodated in the first impeller chamber and a second impeller accommodated in the second impeller chamber. The drive shaft is accommodated in the housing and extends in the axial direction of the drive shaft to connect the first and second impellers and the electric motor. The housing has an outlet and an inlet. The outlet communicates with the first impeller chamber, and the inlet communicates with the second impeller chamber. The compressed fluid passage is disposed outside the housing and connects the outlet and the inlet.

In such a turbo fluid machine, the first and second impellers rotate with rotation of the electric motor to compress fluid in two steps. Specifically, the first impeller compresses the fluid inside the first impeller chamber to produce first compressed fluid. The first compressed fluid is supplied from the first impeller chamber to the second impeller chamber through the compressed fluid passage. Then, the second impeller compresses the first compressed fluid to produce second compressed fluid.

In the above-described turbo fluid machine, when the first impeller and the to second impeller rotate, a rotational component is applied to the first compressed fluid and the second compressed fluid. Then, in such a turbo fluid machine, the first compressed fluid having the rotational component is supplied to the second impeller chamber through the compressed fluid passage. Thus, when the second impeller compresses the first compressed fluid to produce the second compressed fluid, it is difficult to increase a pressure of the second compressed fluid due to the rotational component included in the first compressed fluid. This causes a decrease in compression performance of the fluid.

On the other hand, in the turbo fluid machine of Japanese Patent Application Publication No. H08-200296, a division plate is provided inside a compressed fluid passage. The division plate has, in its central portion, an opening into which first compressed fluid flows. The division plate has an annular shape. The division plate includes a plurality of return guide vanes. The return guide vanes are arranged in a circumferential direction of the division plate.

In such a turbo fluid machine, the first compressed fluid flowing through the compressed fluid passage is guided from an outer circumferential side of the division plate into the opening by the return guide vanes and flows from the opening toward an inlet. Thus, in this turbo fluid machine, the first compressed fluid is straightened by the return guide vanes of the division plate and supplied to the second impeller chamber. As a result, in this turbo fluid machine, a pressure of the second compressed fluid increases sufficiently.

This kind of turbo fluid machine needs to be downsized in order that the turbo fluid machine is easily mounted on a vehicle or the like. However, in the turbo fluid machine of Japanese Patent Application Publication No. H08-200296, downsizing of the division plate is difficult due to a complicated configuration of the division plate, and it is necessary to increase in size to secure a space for the division plate. Thus, the downsizing of this kind of turbo fluid machine is difficult. In addition, a manufacturing cost of the turbo fluid machine increases due to the complicated configuration of the division plate.

The present disclosure, which has been made in light of the above-mentioned problem, is directed to providing a turbo fluid machine reducing a size and a manufacturing cost thereof with a high compression performance.

SUMMARY

In accordance with an aspect of the present disclosure, there is provided a turbo fluid machine that includes: a housing including an impeller chamber and a motor chamber; an electric motor accommodated in the motor chamber; an impeller that is accommodated in the impeller chamber and compresses fluid with rotation of the electric motor; and a drive shaft connecting the impeller and the electric motor in the housing. The impeller chamber includes a first impeller chamber and a second impeller chamber distanced from each other in an axial direction of the drive shaft. The impeller includes: a first impeller that is accommodated in the first impeller chamber and compresses the fluid to produce first compressed fluid; and a second impeller that is accommodated in the second impeller chamber and compresses the first compressed fluid to produce second compressed fluid. The turbo fluid machine further includes: a compressed fluid passage through which the first compressed fluid is supplied to the second impeller chamber; and a plurality of flow straightening passages that extends inside the compressed fluid passage in a direction in which the compressed fluid passage extends, and through which the first compressed fluid is straightened and supplied to the second impeller chamber.

Other aspects and advantages of the disclosure will become apparent from the following description, taken in conjunction with the accompanying drawings, illustrating by way of example the principles of the disclosure.

BRIEF DESCRIPTION OF THE DRAWINGS

The disclosure, together with objects and advantages thereof, may best be understood by reference to the following description of the embodiments together with the accompanying drawings in which:

FIG. 1 is a cross-sectional view of a turbo fluid machine according to a first embodiment;

FIG. 2 is an enlarged cross-sectional view of a main part of the turbo fluid machine according to the first embodiment, illustrating “X” of FIG. 1 ;

FIG. 3 is a cross-sectional view of the turbo fluid machine according to the first embodiment, taken along a line III-III of FIG. 2 ;

FIG. 4A is a schematic view of a cross-sectional area of a compressed fluid passage in the turbo fluid machine according to the first embodiment, and FIG. 4B is a schematic view of a cross-sectional area of a flow straightening passage in the turbo fluid machine according to the first embodiment;

FIG. 5 is an enlarged cross-sectional view of a main part of a turbo fluid machine according to a second embodiment, illustrating a compressed fluid passage, a flow straightening passage, and a cooling portion, as with FIG. 2 ;

FIG. 6 is a cross-sectional view of the turbo fluid machine according to the second embodiment, taken along a line VI-VI of FIG. 5 ;

FIG. 7A is a schematic view of a cross-sectional area of a compressed fluid passage in the turbo fluid machine according to the second embodiment, and FIG. 7B is a schematic view of a cross-sectional area of a flow straightening passage in the turbo fluid machine according to the second embodiment;

FIG. 8 is a cross-sectional view of the turbo fluid machine according to the second embodiment, taken along a line VIII-VIII of FIG. 5 ;

FIG. 9 is a cross-sectional view of a turbo fluid machine according to a third embodiment, as seen in the same direction as that of FIG. 3 ; and

FIG. 10A is a schematic view of a cross-sectional area of a compressed fluid passage in the turbo fluid machine according to the third embodiment, and FIG. 10B is a schematic view of a cross-sectional area of a flow straightening passage in the turbo fluid machine according to the third embodiment.

DETAILED DESCRIPTION OF THE EMBODIMENTS

The following will describe first to third embodiments of the present disclosure with reference to drawings. A turbo fluid machine of each of the first to third embodiments is mounted on a fuel cell vehicle, and connected to a fuel cell stack. The fuel cell vehicle and the fuel cell stack are not illustrated.

As illustrated in FIGS. 1 to 3 , the turbo fluid machine of the first embodiment includes a housing 1, an electric motor 3, a drive shaft 5, an impeller including a first impeller 7 and a second impeller 8, a compressed fluid passage 9, and seven first flow straightening passages 31 a to 31 g. Each of the first flow straightening passages 31 a to 31 g is an example of a “flow straightening passage” of the present disclosure.

In the present embodiment, a solid arrow of FIG. 1 indicates a front-rear direction of the turbo fluid machine. The front-rear direction corresponds to an example of an “axial direction of a drive shaft” of the present disclosure. Terms of “front/rear” and “forward/rearward” indicate the front-rear direction of the turbo fluid machine. An orientation of the turbo fluid machine is appropriately changeable depending on a vehicle on which the turbo fluid machine is mounted.

The housing 1 is made of aluminum alloy. As illustrated in FIG. 1 , the housing 1 includes a motor housing 10, a first plate 11, a second plate 12, a third plate 13, a first compressor housing 14, and a second compressor housing 15.

The motor housing 10 has an end wall 10 a and a peripheral wall 10 b. The end wall 10 a is disposed at a rear end of the motor housing 10 and extends in a radial direction of the motor housing 10. The end wall 10 a has a first end surface 101 facing to the front and a second end surface 102 that is opposite to the first end surface 101 and faces to the rear. The second end surface 102 forms a rear end surface of the motor housing 10.

The peripheral wall 10 b is formed integrally with the end wall 10 a and extends tubularly forward from the end wall 10 a. The peripheral wall 10 b has, in its front part, an opening. The end wall 10 a and the peripheral wall 10 b define the motor housing 10 with a bottomed tubular shape. A flange portion 10 c is formed at a front end of the peripheral wall 10 b. The flange portion 10 c protrudes outward from the peripheral wall 10 b in the radial direction of the motor housing 10.

The first plate 11 is disposed in front of the motor housing 10. The first plate 11 includes a first front surface 11 a positioned at the front and a first rear surface 11 b positioned at the rear. The first plate 11 allows the first rear surface 11 b to be in contact with the flange portion 10 c and is connected to the flange portion 10 c. As a result, the first plate 11 closes the opening of the peripheral wall 10 b. Thus, the end wall 10 a, the peripheral wall 10 b, and the first rear surface 11 b define a motor chamber 30 inside the motor housing 10.

The first plate 11 includes a first boss portion 11 c, a first recess 11 d, and a first shaft hole 11 e. The first boss portion 11 c protrudes cylindrically rearward from the first rear surface 11 b, and extends inside the motor chamber 30. A first radial bearing 21 a is provided inside the first boss portion 11 c.

The first front surface 11 a is recessed rearward to form the first recess 11 d. A first thrust bearing 23 a and a second thrust bearing 23 b are provided inside the first recess 11 d. The first shaft hole 11 e is positioned in a central portion of the first plate 11 and extends through the first plate 11 in the front-rear direction. Thus, the first shaft hole 11 e communicates with the first recess 11 d at a front end of the first shaft hole 11 e, and communicates with the first boss portion 11 c at a rear end of the first shaft hole 11 e. The first boss portion 11 c, the first recess 11 d, and the first shaft hole 11 e are formed coaxially with each other.

The end wall 10 a of the motor housing 10 includes a second boss portion 10 d and a second shaft hole 10 e. The second boss portion 10 d protrudes cylindrically forward from the first end surface 101 and extends inside the motor chamber 30. A second radial bearing 21 b is provided inside the second boss portion 10 d. The second shaft hole 10 e is disposed in a central portion of the end wall 10 a and extends through the end wall 10 a in the front-rear direction. Thus, the second shaft hole 10 e communicates with the second boss portion 10 d at a front end of the second shaft hole 10 e. The second boss portion 10 d and the second shaft hole 10 e are formed coaxially with the first boss portion 11 c, the first recess 11 d, and the first shaft hole 11 e.

The second plate 12 is disposed in front of the first plate 11. The second plate 12 includes a second front surface 12 a on a front side of the second plate 12 and a second rear surface 12 b on a rear side of the second plate 12. The second plate 12 allows the second rear surface 12 b to be in contact with the first front surface 11 a and is connected to the first plate 11.

The second plate 12 includes a second recess 12 c and a third shaft hole 12 d. The second front surface 12 a is recessed rearward to form the second recess 12 c. The second recess 12 c has a diameter smaller than that of the first recess 11 d. A first sealing member 25 a is provided inside the second recess 12 c. The third shaft hole 12 d is disposed in a central portion of the second plate 12 and extends through the second plate 12 in the front-rear direction. Thus, the third shaft hole 12 d communicates with the second recess 12 c at a front end of the third shaft hole 12 d, and communicates with the first recess 11 d at a rear end of the third shaft hole 12 d. The second recess 12 c and the third shaft hole 12 d are formed coaxially with the first boss portion 11 c, the first recess 11 d, and the first shaft hole 11 e.

The third plate 13 is disposed in the rear of the motor housing 10. The third plate 13 includes a third front surface 13 a on a front side of the third plate 13 and a third rear surface 13 b on a rear side of the third plate 13. The third plate 13 allows the third front surface 13 a to be in contact with the second end surface 102 of the end wall 10 a and is connected to the motor housing 10.

The third plate 13 includes a third recess 13 c and a fourth shaft hole 13 d. The third rear surface 13 b is recessed forward to form the third recess 13 c. The third recess 13 c has the same diameter as that of the second recess 12 c. A second sealing member 25 b is provided inside the third recess 13 c. The fourth shaft hole 13 d is disposed in a central portion of the third plate 13 and extends through the third plate 13 in the front-rear direction. Thus, the fourth shaft hole 13 d communicates with the second shaft hole 10 e at a front end of the fourth shaft hole 13 d and communicates with the third recess 13 c at a rear end of the fourth shaft hole 13 d. The third recess 13 c and the fourth shaft hole 13 d are formed coaxially with the second boss portion 10 d and the second shaft hole 10 e. That is, the third recess 13 c and the fourth shaft hole 13 d are formed coaxially with the first boss portion 11 c, the first recess 11 d, the first shaft hole 11 e, the second recess 12 c, and the third shaft hole 12 d.

The first compressor housing 14 is disposed in front of the second plate 12. The first compressor housing 14 has a tubular shape. The first compressor housing 14 is in contact with the second front surface 12 a of the second plate 12 and connected to the second plate 12. As a result, the first compressor housing 14 forms a front end portion of the housing 1. The first compressor housing 14 has a first inlet 14 a and a first outlet 14 b.

The first inlet 14 a is formed coaxially with the third shaft hole 12 d and extends inside the first compressor housing 14 in the front-rear direction. A front to end of the first inlet 14 a is opened at a front end surface 140 of the first compressor housing 14. An inlet piping 37 is connected to the first inlet 14 a. Air containing oxygen is drawn into the first inlet 14 a from an outside of the housing 1 through the inlet piping 37. The air is an example of “fluid” of the present disclosure.

The first outlet 14 b extends inside the first compressor housing 14 in its radial direction and is opened at an outer peripheral surface 141 of the first compressor housing 14. A first straight passage 9 a of the compressed fluid passage 9 which will be described later is connected to the first outlet 14 b.

A first impeller chamber 27 a, a first discharge chamber 27 b, and a first diffuser passage 27 c are formed between the first compressor housing 14 and the second front surface 12 a. The first impeller chamber 27 a communicates with the first inlet 14 a. The first discharge chamber 27 b is formed around the first impeller chamber 27 a and extends around an axis of the first inlet 14 a. The first discharge chamber 27 b communicates with the first outlet 14 b. The first impeller chamber 27 a communicates with the first discharge chamber 27 b through the first diffuser passage 27 c. As a result, the first impeller chamber 27 a communicates with the first outlet 14 b through the first diffuser passage 27 c and the first discharge chamber 27 b.

The second compressor housing 15 is disposed in the rear of the third plate 13. The second compressor housing 15 has a tubular shape, as with the first compressor housing 14. The second compressor housing 15 is in contact with the third rear surface 13 b of the third plate 13 and connected to the third plate 13. Thus, the second compressor housing 15 forms a rear end portion of the housing 1. The second compressor housing 15 has a second inlet 15 a and a second outlet 15 b.

The second inlet 15 a is formed coaxially with the first inlet 14 a and extends inside the second compressor housing 15 in the front-rear direction. A rear end of the second inlet 15 a is opened at a rear end surface 150 of the second compressor housing 15. A fourth straight passage 9 d of the compressed fluid passage 9 which will be described later is connected to the second inlet 15 a.

The second outlet 15 b extends inside the second compressor housing 15 in its radial direction, and is opened at the outer peripheral surface 151 of the second compressor housing 15. A discharge piping 39 is connected to the second outlet 15 b. Through the discharge piping 39, the turbo fluid machine is connected to the fuel cell stack.

A second impeller chamber 29 a, a second discharge chamber 29 b, and a second diffuser passage 29 c are formed between the second compressor housing and the third rear surface 13 b. The second impeller chamber 29 a communicates with the second inlet 15 a. The second discharge chamber 29 b is formed around the second impeller chamber 29 a and extends around an axis of the second inlet 15 a. The second discharge chamber 29 b communicates with the second outlet 15 b. The second impeller chamber 29 a communicates with the second discharge chamber 29 b through the second diffuser passage 29 c. As a result, the second impeller chamber 29 a communicates with the second outlet 15 b through the second diffuser passage 29 c and the second discharge chamber 29 b.

As described above, in the housing 1, the first impeller chamber 27 a and the second impeller chamber 29 a are distanced from each other in the front-rear direction, and the motor chamber 30 is disposed between the first impeller chamber 27 a and the second impeller chamber 29 a. The first impeller chamber 27 a and the second impeller chamber 29 a are collectively referred to as an impeller chamber.

The electric motor 3 is accommodated in the motor chamber 30. The electric motor 3 includes a stator 3 a and a rotor 3 b. The stator 3 a has a cylindrical shape, extends in the front-rear direction, and is fixed to an inner peripheral surface of the peripheral wall 10 b. The stator 3 a is connected to a power supplier (not illustrated) provided outside the housing 1. The rotor 3 b whose diameter is smaller than that of the stator 3 a has a cylindrical shape and extends in the front-rear direction. The rotor 3 b is disposed inside the stator 3 a.

The drive shaft 5 has a cylindrical columnar shape and extends in the axial direction of the drive shaft 5, i.e., in the front-rear direction. The drive shaft 5 has a first shaft portion 5 a, a second shaft portion 5 b, a third shaft portion 5 c, a fourth shaft portion 5 d, and a fifth shaft portion 5 e arranged in this order from the front to the rear. The first shaft portion 5 a and the fifth shaft portion 5 e have the same diameter and each have the smallest diameter in the drive shaft 5. The second shaft portion 5 b and the fourth shaft portion 5 d have the same diameter and each have a diameter larger than that of each of the first shaft portion 5 a and the fifth shaft portion 5 e. A front end of the second shaft portion 5 b is connected to the first shaft portion 5 a. A rear end of the fourth shaft portion 5 d is connected to the fifth shaft portion 5 e. The third shaft portion 5 c has the largest diameter in the drive shaft 5. A front end of the third shaft portion 5 c is connected to the second shaft portion 5 b, and a rear end of the third shaft portion 5 c is connected to the fourth shaft portion 5 d.

The drive shaft 5 is inserted into the housing 1, and is rotatable around a shaft axis O. In the drive shaft 5, the first shaft portion 5 a extends inside the first impeller chamber 27 a. The shaft axis O extends in a direction parallel to the front-rear direction of the turbo fluid machine.

The second shaft portion 5 b is inserted into the third shaft hole 12 d and the first shaft hole 11 e, and extends inside the second recess 12 c and the first recess 11 d. The second shaft portion 5 b is inserted into the first sealing member 25 a inside the second recess 12 c. As a result, the first sealing member 25 a seals a gap between the first impeller chamber 27 a and, the first recess 11 d and the motor chamber 30. The second shaft portion 5 b is inserted into the first thrust bearing 23 a and the second thrust bearing 23 b inside the first recess 11 d, and is press-fitted into a support plate 51. The support plate 51 is disposed between the first thrust bearing 23 a and the second thrust bearing 23 b. Thus, the support plate 51 holds the first thrust bearing 23 a between the second rear surface 12 b and the support plate 51 in the front-rear direction, and holds the second thrust bearing 23 b between a wall surface of the first recess 11 d and the support plate 51 in the front-rear direction.

The third shaft portion 5 c extends inside the motor chamber 30. The third shaft portion 5 c is inserted into and fixed to the rotor 3 b. The third shaft portion 5 c is supported by the first radial bearing 21 a inside the first boss portion 11 c, and supported by the second radial bearing 21 b inside the second boss portion 10 d.

The fourth shaft portion 5 d is inserted into the fourth shaft hole 13 d and extends inside the third recess 13 c. The fourth shaft portion 5 d is inserted into the second sealing member 25 b inside the third recess 13 c. As a result, the second sealing member 25 b seals a gap between the second impeller chamber 29 a and the motor chamber 30. The fifth shaft portion 5 e extends inside the second impeller chamber 29 a.

The first impeller 7 is accommodated in the first impeller chamber 27 a. The first impeller 7 is formed into a substantially conical shape whose diameter gradually increases from the front to the rear. On the other hand, the second impeller 8 is accommodated in the second impeller chamber 29 a. The second impeller 8 is symmetrical to the first impeller 7 in the front-rear direction. That is, the second impeller 8 is formed into a substantially conical shape whose diameter gradually decreases from the front to the rear. The first impeller 7 is made of aluminum alloy, and the second impeller 8 is made of steel.

The first impeller 7 is fixed to the first shaft portion 5 a of the drive shaft 5. The second impeller 8 is fixed to the fifth shaft portion 5 e of the drive shaft 5. Thus, the drive shaft 5 connects the first and second impellers 7, 8 and the electric motor 3.

The compressed fluid passage 9 is provided separately from the housing 1 and disposed outside the housing 1. The compressed fluid passage 9 includes a first straight passage 9 a, a second straight passage 9 b, a third straight passage 9 c, a fourth straight passage 9 d, a first corner passage 9 e, a second corner passage 9 f, and a third corner passage 9 g. The compressed fluid passage 9 including the first to fourth straight passages 9 a to 9 d and the first to third corner passages 9 e to 9 g is formed of a metal piping having a cylindrical shape. First compressed air which will be described later flows through the compressed fluid passage 9.

The first to fourth straight passages 9 a to 9 d extend straight in their longitudinal directions. The first compressed air flows through the first to fourth straight passages 9 a to 9 d in their longitudinal directions. As illustrated in FIG. 2 and FIG. 3 , an inner diameter of the third straight passage 9 c corresponds to a first length L1. An inner diameter of each of the first, second, and fourth straight passages 9 a, 9 b, 9 d of FIG. 1 also corresponds to the first length L1. The first to third corner passages 9 e to 9 g are each bent at a substantially right angle. An inner diameter of each of the first to third corner passages 9 e to 9 g is larger than that of each of the first to fourth straight passages 9 a to 9 d. The first to fourth straight passages 9 a to 9 d extend inside the first to third corner passages 9 e to 9 g.

In the compressed fluid passage 9, the first straight passage 9 a, the first corner passage 9 e, the second straight passage 9 b, the second corner passage 9 f, the third straight passage 9 c, the third corner passage 9 g, and the fourth straight passage 9 d are arranged in this order in a flowing direction of the first compressed air which will be described later. Then, in the compressed fluid passage 9, one end of the first straight passage 9 a is connected to the first outlet 14 b. Through the first corner passage 9 e, the other end of the first straight passage 9 a is connected to one end of the second straight passage 9 b. Through the second corner passage 9 f, the other end of the second straight passage 9 b is connected to one end of the third straight passage 9 c. Through the third corner passage 9 g, the other end of the third straight passage 9 c is connected to one end of the fourth straight passage 9 d. The other end of the fourth straight passage 9 d is connected to the second inlet 15 a. The compressed fluid passage 9 connects the first outlet 14 b and the second inlet 15 a as described above. The first to fourth straight passages 9 a to 9 d each form a straight portion of the compressed fluid passage 9, and the first to third corner passages 9 e to 9 g each form a corner portion of the compressed fluid passage 9.

Here, in the compressed fluid passage 9, a distance from the third straight passage 9 c to the second inlet 15 a is smaller than that from the first outlet 14 b to the third straight passage 9 c. That is, in the compressed fluid passage 9, the third straight passage 9 c is disposed at a position closer to the second inlet 15 a than to the first outlet 14 b, i.e., at a position closer to the second impeller chamber 29 a than to the first impeller chamber 27 a. The compressed fluid passage 9 may have any shape as appropriate.

As illustrated in FIG. 1 to FIG. 3 , the first flow straightening passages 31 a to 31 g are provided inside the third straight passage 9 c. As a result, in the compressed fluid passage 9, the first flow straightening passages 31 a to 31 g are each disposed at a position closer to the second impeller chamber 29 a than to the first impeller chamber 27 a.

As illustrated in FIG. 2 and FIG. 3 , the first flow straightening passages 31 a to 31 g have the same configuration, and are each formed of a cylindrical body that is made of metal and extends straight in a direction parallel to the longitudinal direction of the third straight passage 9 c. Specifically, the first flow straightening passages 31 a to 31 g are each formed of a known pipe made of metal. Thus, the first compressed airflows through the first flow straightening passages 31 a to 31 g. A length of each of the first flow straightening passages 31 a to 31 g in a longitudinal direction thereof is smaller than that of the third straight passage 9 c in the longitudinal direction thereof. Any number of the first flow straightening passages 31 a to 31 g may be provided appropriately as long as a plurality of first flow straightening passages is provided. The first flow straightening passages 31 a to 31 g may be formed of a cylindrical body made of resin.

An inner diameter of each of the first flow straightening passages 31 a to 31 g corresponds to a second length L2. The second length L2 is smaller than the first length L1 corresponding to the inner diameter of the compressed fluid passage 9. Specifically, the second length L2 is smaller than one-third of the first length L1. Thus, as illustrated in FIG. 4B, a second passage cross-sectional area S2 that is a cross-sectional area of each of the first flow straightening passages 31 a to 31 g is smaller than a first passage cross-sectional area S1 that is a cross-sectional area of the third straight passage 9 c of FIG. 4A. Furthermore, a sum of seven second passage cross-sectional areas S2 corresponding to the number of the first flow straightening passages 31 a to 31 g is smaller than the first passage cross-sectional area S1.

As illustrated in FIG. 3 , the first flow straightening passages 31 a to 31 g are bonded to each other while the first flow straightening passage 31 a is disposed in a central portion of the compressed fluid passage 9 and bonded to the first flow straightening passages 31 b to 31 g arranged in a circumferential direction of the first flow straightening passage 31 a. The first flow straightening passages 31 a to 31 g are inserted into the third straight passage 9 c and are bonded and fixed to an inner peripheral surface 901 of the third straight passage 9 c. As a result, the first flow straightening passages 31 a to 31 g are provided inside the third straight passage 9 c.

In the above-described turbo fluid machine, the power supplier supplies power to the electric motor 3 illustrated in FIG. 1 to operate the electric motor 3, which causes the drive shaft 5 to rotate around the shaft axis O. With rotation of the electric motor 3, the first impeller 7 rotates around the shaft axis O inside the first impeller chamber 27 a, and the second impeller 8 rotates around the shaft axis O inside the second impeller chamber 29 a. Thus, in the turbo fluid machine, the first impeller 7 and the second impeller 8 compress air drawn from the first inlet 14 a in two steps.

Specifically, the first impeller 7 compresses the air drawn from the first inlet 14 a into the first impeller chamber 27 a to produce first compressed air. Then, the first compressed air flows from the first impeller chamber 27 a toward the first discharge chamber 27 b. That is, a pressure of the first compressed air is higher than that of the air drawn from the first inlet 14 a into the first impeller chamber 27 a.

The first compressed air is discharged from the first outlet 14 b into the compressed fluid passage 9, flows through the first straight passage 9 a, the first corner passage 9 e, the second straight passage 9 b, the second corner passage 9 f, the third straight passage 9 c, the first flow straightening passages 31 a to 31 g, the third corner passage 9 g, and the fourth straight passage 9 d in this order, and is supplied from the second inlet 15 a into the second impeller chamber 29 a.

The second impeller 8 further compresses the first compressed air supplied into the second impeller chamber 29 a to produce second compressed air having a pressure higher than that of the first compressed air. Then, the second compressed air flows from the second impeller chamber 29 a toward the second discharge chamber 29 b. As described above, the second compressed air is discharged from the second outlet 15 b into the discharge piping 39, and supplied to a cathode of the fuel cell stack through the discharge piping 39.

In the turbo fluid machine of the present embodiment, the first impeller 7 and the second impeller 8 rotate around the shaft axis O, so that a rotational component is applied to each of the first compressed air and the second compressed air. In the turbo fluid machine, the first compressed air flowing through the compressed fluid passage 9 is straightened in the first flow straightening passages 31 a to 31 g, and is supplied into the second impeller chamber 29 a.

That is, as illustrated by a dashed arrow of FIG. 2 , the first compressed air discharged from the first outlet 14 b passes through the first straight passage 9 a, the first corner passage 9 e, the second straight passage 9 b, the second corner passage 9 f, and the third straight passage 9 c, and reaches the first flow straightening passages 31 a to 31 g. Then, the first compressed air having reached the first flow straightening passages 31 a to 31 g flows through the first flow straightening passages 31 a to 31 g. The inner diameter of each of the first flow straightening passages 31 a to 31 g corresponds to the second length L2 that is smaller than the first length L1 corresponding to the inner diameter of the third straight passage 9 c. Thus, a diameter of each of the first flow straightening passages 31 a to 31 g is smaller than that of the third straight passage 9 c, and the second passage cross-sectional area S2 is smaller than the first passage cross-sectional area S1. That is, an internal space of each of the first flow straightening passages 31 a to 31 g is narrower than that of the third straight passage 9 c.

Thus, the first compressed air is gradually straightened while flowing through the first flow straightening passages 31 a to 31 g, which reduces the rotational component of the first compressed air. As a result, the first compressed air having passed through the first flow straightening passages 31 a to 31 g flows through the third corner passage 9 g and the fourth straight passage 9 d in a state where the rotational component of the first compressed air is reduced as compared with that of the first compressed air not having reached the first flow straightening passages 31 a to 31 g. Thus, the first compressed air is supplied from the second inlet 15 a into the second impeller chamber 29 a in a state where the rotational component of the first compressed air is reduced as compared with that of the first compressed air when discharged from the first outlet 14 b.

As described above, in the turbo fluid machine of the present embodiment, when the second impeller 8 compresses the first compressed air to produce the second compressed air, the pressure of the second compressed air increases sufficiently. Thus, in the turbo fluid machine of the present embodiment, the second compressed air with high pressure is supplied to the cathode of the fuel cell stack. To be exact, part of the first compressed air flows through gaps between the first flow straightening passages 31 a to 31 g and between each of the first flow straightening passages 31 a to 31 g and the third straight passage 9 c. Then, the part of the first compressed air having flowed through the gaps and the first compressed air having flowed through the first flow straightening passages 31 a to 31 g are supplied into the second impeller chamber 29 a and compressed by the second impeller 8.

Here, each of the first flow straightening passages 31 a to 31 g is formed of the cylindrical body that extends straight and has the second passage cross-sectional area S2 smaller than the first passage cross-sectional area S1, specifically, of a known pipe. Furthermore, a sum of the seven second passage cross-sectional areas S2 corresponding to the number of the first flow straightening passages 31 a to 31 g is smaller than the first passage cross-sectional area S1. As a result, in the turbo fluid machine of the present embodiment, the first compressed air is suitably straightened while flowing through the first flow straightening passages 31 a to 31 g, although a configuration of each of the first flow straightening passages 31 a to 31 g is simplified to achieve downsizing and reduction of a manufacturing cost of the turbo fluid machine. In the turbo fluid machine of the present embodiment, an increase in size of the third straight passage 9 c, then an increase in size of the compressed fluid passage 9, is suppressed, although the first flow straightening passages 31 a to 31 g are provided inside the compressed fluid passage 9.

Therefore, in the turbo fluid machine of the first embodiment, the downsizing and the reduction of the manufacturing cost of the turbo fluid machine are achieved with a high compression performance.

In particular, the first flow straightening passages 31 a to 31 g are provided in the third straight passage 9 c at a position closer to the second impeller chamber 29 a than to the first impeller chamber 27 a. Thus, in the turbo fluid machine of the present embodiment, a pressure drop of the first compressed air is minimized as much as possible during a period of time until the first compressed air passes through the first flow straightening passages 31 a to 31 g and is supplied from the second inlet 15 a to the second impeller chamber 29 a.

Since the first flow straightening passages 31 a to 31 g are each formed of the cylindrical body, the first compressed air suitably flows through the first flow straightening passages 31 a to 31 g as compared with a case where the first flow straightening passages 31 a to 31 g are each formed of a rectangular tubular body, for example. Therefore, it is possible to reduce the pressure drop of the first compressed air flowing through the first flow straightening passages 31 a to 31 g.

Second Embodiment

In a turbo fluid machine of a second embodiment, the first impeller 7 and the second impeller 8 (see FIG. 1 ) are each made of aluminum alloy. As illustrated in FIG. 5 and FIG. 6 , in the turbo fluid machine of the present embodiment, seven second flow straightening passages 33 a to 33 g are provided inside the third straight passage 9 c. Each of the second flow straightening passages 33 a to 33 g is an example of a “flow straightening passage” of the present disclosure.

The second flow straightening passages 33 a to 33 g have the same configuration. As illustrated in FIG. 5 , the second flow straightening passages 33 a to 33 g are each formed of a cylindrical body that is made of metal and extends straight in a direction parallel to the longitudinal direction of the third straight passage 9 c. Specifically, the second flow straightening passages 33 a to 33 g are each formed of a known pipe made of metal. As a result, the first compressed air flows through the second flow straightening passages 33 a to 33 g. Any number of the second flow straightening passages 33 a to 33 g may be appropriately set as long as a plurality of second flow straightening passages is provided. The second flow straightening passages 33 a to 33 g may be formed of a cylindrical body made of resin.

Here, an inner diameter of each of the second flow straightening passages 33 a to 33 g corresponds to a third length L3. The third length L3 is smaller than the second length L2 corresponding to the inner diameter of each of the first flow straightening passages 31 a to 31 g of the first embodiment. Thus, as illustrated in FIG. 7B, a third passage cross-sectional area S3 that is a cross-sectional area of each of the second flow straightening passages 33 a to 33 g is smaller than the first passage cross-sectional area S1 that is a cross-sectional area of the third straight passage 9 c illustrated in FIG. 7A. Furthermore, a sum of seven third passage cross-sectional areas S3 corresponding to the number of the second flow straightening passages 33 a to 33 g is smaller than the first passage cross-sectional area S1. Features of the second flow straightening passages 33 a to 33 g other than the above-described feature of the present embodiment are the same as those of the first flow straightening passages 31 a to 31 g. A mounting of the second flow straightening passages 33 a to 33 g to the third straight passage 9 c will be described later.

As illustrated in FIG. 5 , in the turbo fluid machine of the present embodiment, the compressed fluid passage 9 has a cooling portion 41. The cooling portion 41 includes a first connection port 41 a, a second connection port 41 b, a supply piping 41 c, a return piping 41 d, a pump 41 e, a first partition wall 41 f, a second partition wall 41 g, and a cooling chamber 41 h.

The first connection port 41 a and the second connection port 41 b are distanced from each other in the third straight passage 9 c. Specifically, the first connection port 41 a and the second connection port 41 b are each disposed at a position where each of the second flow straightening passages 33 a to 33 g is provided in the third straight passage 9 c. Then, the first connection port 41 a is formed downstream in a flowing direction of the first compressed air relative to the second connection port 41 b. The first connection port 41 a and the second connection port 41 b each extend into the third straight passage 9 c in its radial direction, which allows an inside and an outside of the third straight passage 9 c to communicate with each other.

One end of the supply piping 41 c is connected to the first connection port 41 a, and the other end of the supply piping 41 c is connected to a radiator (not illustrated) of the vehicle. One end of the return piping 41 d is connected to the radiator, and the other end of the return piping 41 d is connected to the second connection port 41 b. Cooling liquid 43 (see FIG. 8 ) such as water and long life coolant flows through the supply piping 41 c and the return piping 41 d. The pump 41 e illustrated in FIG. 5 is provided in the supply piping 41 c. Through the supply piping 41 c and the return piping 41 d, the cooling liquid 43 is circulated through the cooling chamber 41 h and the radiator. The pump 41 e may be provided in the return piping 41 d.

The first partition wall 41 f and the second partition wall 41 g are each made of resin such as synthetic rubber and have the same configuration. The following will describe the first partition wall 41 f. As illustrated in FIG. 6 , the first partition wall 41 f has a disc shape, and a diameter of the first partition wall 41 f corresponds to the first length L1 that is the same length as the inner diameter of the third straight passage 9 c. Seven mounting holes 411 to 417 extend through the first partition wall 41 f. The first partition wall 41 f and the second partition wall 41 g may be made of metal.

As illustrated in FIG. 5 , the first partition wall 41 f and the second partition wall 41 g are provided inside the third straight passage 9 c and distanced from each other in the flowing direction of the first compressed air. Specifically, in the third straight passage 9 c, the first partition wall 41 f is provided upstream in the flowing direction of the first compressed air relative to the second connection port 41 b, and the second partition wall 41 g is provided downstream in the flowing direction of the first compressed air relative to the first connection port 41 a. The first partition wall 41 f and the second partition wall 41 g are in close contact with and bonded to the inner peripheral surface 901 of the third straight passage 9 c. Thus, the first partition wall 41 f and the second partition wall 41 g partition the inside of the third straight passage 9 c.

The cooling chamber 41 h is formed between the first partition wall 41 f, the second partition wall 41 g and the inner peripheral surface 901 in the third straight passage 9 c. The first partition wall 41 f and the second partition wall 41 g seal a gap between an inside and an outside of the cooling chamber 41 h. The supply piping 41 c is connected to the cooling chamber 41 h via the first connection port 41 a, and the return piping 41 d is connected to the cooling chamber 41 h via the second connection port 41 b.

The second flow straightening passages 33 a to 33 g are inserted into mounting holes 411 to 417 of the first partition wall 41 f and the second partition wall 41 g, respectively. Specifically, as illustrated in FIG. 6 , the second flow straightening passage 33 a is inserted into the mounting hole 411, the second flow straightening passage 33 b is inserted into the mounting hole 412, the second flow straightening passage 33 c is inserted into the mounting hole 413, the second flow straightening passage 33 d is inserted into the mounting hole 414, the second flow straightening passage 33 e is inserted into the mounting hole 415, the second flow straightening passage 33 f is inserted into the mounting hole 416, and the second flow straightening passage 33 g is inserted into the mounting hole 417. As a result, the second flow straightening passages 33 a to 33 g are fixed to the first partition wall 41 f and the second partition wall 41 g in a state where the second flow straightening passage 33 a is positioned in a central portion of the third straight passage 9 c and the second flow straightening passages 33 b to 33 g are arranged in a circumferential direction of the second flow straightening passage 33 a.

As described above, the second flow straightening passages 33 a to 33 g are provided inside the cooling chamber 41 h and fixed to the first partition wall 41 f and the second partition wall 41 g. Here, in the turbo fluid machine of the present embodiment, gaps between the second flow straightening passages 33 a to 33 g and a gap between each of the second flow straightening passages 33 a to 33 g and the inner peripheral surface 901 of the third straight passage 9 c are widened as compared with those of the turbo fluid machine of the first embodiment. Features other than the above-described feature of the turbo fluid machine of the present embodiment are the same as those of the turbo fluid machine of the first embodiment. The same elements are designated by the same reference numerals, and the redundant descriptions thereof are omitted.

In the turbo fluid machine of the present embodiment, the first compressed air having reached the second flow straightening passages 33 a to 33 g flows through the second flow straightening passages 33 a to 33 g. As a result, in the turbo fluid machine of the present embodiment, the first compressed air is supplied from the second inlet 15 a into the second impeller chamber 29 a in a state where the rotational component of the first compressed air is reduced, as in the turbo fluid machine of the first embodiment.

In the turbo fluid machine of the present embodiment, as illustrated in FIG. 8 , the pump 41 e is operated so that the cooling liquid 43 flows from the supply piping 41 c into the cooling chamber 41 h. Then, in the cooling chamber 41 h, heat is exchanged between the first compressed air flowing through the second flow straightening passages 33 a to 33 g and the cooling liquid 43. Thus, the cooling portion 41 cools the first compressed air flowing through the second flow straightening passages 33 a to 33 g.

In the cooling portion 41, the first connection port 41 a is provided downstream in the flowing direction of the first compressed air relative to the second connection port 41 b. Therefore, as shown by a solid arrow of FIG. 5 , the cooling liquid 43 having flowed from the supply piping 41 c into the cooling chamber 41 h flows upstream in the flowing direction of the first compressed air, specifically, flows toward the second connection port 41 b and the return piping 41 d. Then, the flowing direction of the first compressed air flowing through the second flow straightening passages 33 a to 33 g is opposite to a flowing direction of the cooling liquid 43 flowing inside the cooling chamber 41 h. Thus, the heat is suitably exchanged between the first compressed air flowing through the second flow straightening passages 33 a to 33 g and the cooling liquid 43, so that the cooling portion 41 cools the first compressed air sufficiently.

As described above, in the turbo fluid machine of the present embodiment, since the first compressed air is cooled and supplied into the second impeller chamber 29 a, the second impeller 8 need not have an excessive high heat resistance. Thus, in the turbo fluid machine of the present embodiment, the second impeller 8 is made of aluminum alloy, which reduces a weight of the second impeller 8 and reduces a manufacturing cost of the turbo fluid machine.

In the turbo fluid machine of the present embodiment, the cooling portion 41 cools the first compressed air, which prevents the second compressed air from increasing a temperature thereof. Therefore, it is not necessary to provide a cooling portion for cooling the second compressed air. In the turbo fluid machine of the present embodiment, it is prevented that the temperature of the compressed fluid passage 9 is increased by the first compressed air, which further prevents the housing 1 from increasing a temperature thereof due to heat of the compressed fluid passage 9. Operations other than the above-described operation of the turbo fluid machine of the present embodiment are the same as those of the turbo fluid machine of the first embodiment.

Third Embodiment

As illustrated in FIG. 9 , in a turbo fluid machine of a third embodiment, four third flow straightening passages 35 a to 35 d are provided in the third straight passage 9 c. Each of the third flow straightening passages 35 a to 35 d is an example of a “flow straightening passage” of the present disclosure. In the turbo fluid machine of the present embodiment, a division plate 45 is provided inside the third straight passage 9 c.

The division plate 45 is made of metal, extends in a cross shape in the radial direction of the third straight passage 9 c, and extends straight in a longitudinal direction of the division plate 45 parallel to the third straight passage 9 c. Here, a length of the division plate 45 in the radial direction of the third straight passage 9 c is equal to the first length L1 corresponding to the inner diameter of the third straight passage 9 c. A length of the division plate 45 in its longitudinal direction is the same as the above-described length of each of the first flow straightening passages 31 a to 31 g, which is not illustrated. The division plate 45 may have any shape as appropriate. The division plate 45 may be made of resin.

The division plate 45 divides the third straight passage 9 c into the third flow straightening passages 35 a to 35 d inside the third straight passage 9 c. Since the division plate 45 extends straight in its longitudinal direction parallel to the third straight passage 9 c, each of the third flow straightening passages 35 a to 35 d also extends straight in its longitudinal direction parallel to the third straight passage 9 c.

A cross section of each of the third flow straightening passages 35 a to 35 d in a direction perpendicular to the flowing direction of the first compressed air has a circular sector shape in which the third straight passage 9 c is substantially divided into four parts. Thus, as illustrated in FIG. 10B, a fourth passage cross-sectional area S4 that is a cross-sectional area of each of the third flow straightening passages 35 a to 35 d is smaller than the first passage cross-sectional area S1 that is a cross-sectional area of the third straight passage 9 c illustrated in FIG. 10A. A sum of four fourth passage cross-sectional areas S4 corresponding to the number of the third flow straightening passages 35 a to 35 d is smaller than the first passage cross-sectional area S1. Features other than the above-described feature of the turbo fluid machine of the third embodiment are the same as those of the turbo fluid machine of the first embodiment.

In the turbo fluid machine of the present embodiment, the first compressed air having reached the third flow straightening passages 35 a to 35 d flows through the third flow straightening passages 35 a to 35 d. As a result, in the turbo fluid machine of the present embodiment, the first compressed air is supplied from the second inlet 15 a into the second impeller chamber 29 a in a state where the rotational component of the first compressed air is reduced. In the turbo fluid machine of the present embodiment, the division plate 45 is provided inside the third straight passage 9 c, which easily arranges the third flow straightening passages 35 a to 35 d inside the third straight passage 9 c. Thus, in the turbo fluid machine of the present embodiment, a configuration of each of the third flow straightening passages 35 a to 35 d is simplified. Operations other than the above-described operation of the turbo fluid machine of the third embodiment are the same as those of the turbo fluid machine of the first embodiment.

As described above, although the present disclosure has been described in accordance with the first to third embodiments, the present disclosure is not limited by the first to third embodiments and may be appropriately modified without departing from the scope of the disclosure.

For example, in the turbo fluid machine of the first embodiment, although the first flow straightening passages 31 a to 31 g are provided in the third straight passage 9 c of the compressed fluid passage 9, the first flow straightening passages 31 a to 31 g may be provided in the first straight passage 9 a, the fourth straight passage 9 d, or the like. The same applies to the turbo fluid machine of each of the second and third embodiments.

In the turbo fluid machine of the first embodiment, the first flow straightening passages 31 a to 31 g may be provided in a plurality of portions of the compressed fluid passage 9. The same applies to the turbo fluid machine of each of the second and third embodiments.

In the turbo fluid machine of each of the first to third embodiments, the compressed fluid passage 9 may be formed integrally with the housing 1 in its inside.

In the turbo fluid machine of each of the first to third embodiments, although air serves as “fluid” of the present disclosure, refrigerant used for air conditioning may serve as the “fluid” of the present disclosure.

INDUSTRIAL APPLICABILITY

The present disclosure is applicable to a fuel cell system, an air conditioner, and the like. 

What is claimed is:
 1. A turbo fluid machine comprising: a housing including an impeller chamber and a motor chamber; an electric motor accommodated in the motor chamber, an impeller that is accommodated in the impeller chamber and compresses fluid with rotation of the electric motor; and a drive shaft that is accommodated in the housing and connects the impeller and the electric motor, wherein the impeller chamber includes a first impeller chamber and a second impeller chamber distanced from each other in an axial direction of the drive shaft, the impeller includes: a first impeller that is accommodated in the first impeller chamber and compresses the fluid to produce first compressed fluid; and a second impeller that is accommodated in the second impeller chamber and compresses the first compressed fluid to produce second compressed fluid, and the turbo fluid machine further includes: a compressed fluid passage through which the first compressed fluid is supplied to the second impeller chamber; and a plurality of flow straightening passages that extends inside the compressed fluid passage in a direction in which the compressed fluid passage extends, and through which the first compressed fluid is straightened and supplied to the second impeller chamber.
 2. The turbo fluid machine according to claim 1, wherein each of the flow straightening passages is disposed at a position closer to the second impeller chamber than to the first impeller chamber.
 3. The turbo fluid machine according to claim 1, wherein each of the flow straightening passages is formed of a cylindrical body extending straight.
 4. The turbo fluid machine according to claim 1, wherein the compressed fluid passage includes a cooling portion configured to cool the first compressed fluid flowing through each of the flow straightening passages. 